#!/usr/bin/perl

   use DBI;
   
   $|=1;
   
   $dsn = "DBI:mysql:mydatabase;localhost";
           $dbh = DBI->connect($dsn, 'username', 'password');
   
   if ( !defined $dbh ) {
     exit;
   }
   
   # use the four lines below if the query results
   # in many rows or if you get 'out of memory' errors
   
   #$SQL_QUERY="SET SQL_BIG_TABLES=1";
   #  $cursor = $dbh->prepare( "$SQL_QUERY" );
   #  $cursor->execute;
   #  $cursor->finish;
   
   $SQL_QUERY=<<__CURSOR_1__;
     update table_1
        set col_2 = '$var2',
            col_3 = '$var2'
      where table_1.col_1 = 'X'
__CURSOR_1__
   
   $cursor = $dbh->prepare( "$SQL_QUERY" );
   $cursor->execute;                     
   $cursor->finish;
   $dbh->disconnect;